Re: [PATCH 1/4] seccomp: Provide matching filter for introspection

[Kees Cook]

On Mon, Aug 7, 2017 at 6:03 PM, Tyler Hicks <tyhicks@xxxxxxxxxxxxx> wrote:
>> -static u32 seccomp_run_filters(const struct seccomp_data *sd)
>> +static u32 seccomp_run_filters(const struct seccomp_data *sd,
>> +                            struct seccomp_filter **match)
>>  {
>>       struct seccomp_data sd_local;
>>       u32 ret = SECCOMP_RET_ALLOW;
>
> My version of this patch initialized *match to f here. The reason I did
> that is because if BPF_PROG_RUN() returns RET_ALLOW for all
> filters, I didn't want *match to remain NULL when seccomp_run_filters()
> returns. FILTER_FLAG_LOG nor FILTER_FLAG_KILL_PROCESS would be affected
> by this because they don't care about RET_ALLOW actions but there could
> conceivably be a filter flag in the future that cares about RET_ALLOW
> and not initializing *match to the first filter could result in a latent
> bug for that filter flag.

Very true, yes. I did intentionally adjust this because I wanted to
keep the hot path as untouched as possible.

> I'm fine with not adding the initialization since this is a hot path and
> it doesn't help any of the currently existing/planned filter flags but I
> wanted to at least mention it.

Yeah, and while I doubt I'll want to ever check "match" for RET_ALLOW,
I'll add a big comment there to explain it.

> Reviewed-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxx>

Thanks!

-Kees

-- 
Kees Cook
Pixel Security